I know they scan, but I never see such ads, not only does my browser block them but the text based ones I don't actually read to know what they would be about.
And the ones that do show up I simply ignore and register as 'spam' and nothing more most of the time, who looks at these things? It's all just noise in a sea of crap.

I did come across some ads on sites that detected my area though, that sprung out and I triple blocked those by URL by IP by script and by avoiding the site that presented them forever.